It is common to use abrasives to abrade specified amounts of material from the outer surface of a workpiece to provide a desired workpiece shape and surface finish. In the automotive field, for example, lobes or thrustwalls of camshafts and crankshafts for internal combustion engines must meet exacting standards for geometry and surface finish. If a camshaft or a crankshaft is improperly sized or finished, undesired wear patterns may result.
One manner of finishing the outer peripheral surface of a workpiece, such as a thrustwall, is to provide a shoe having a smooth pressure face against which an abrasive sheet or tape is placed. In some cases, the shoe is provided with conventional honing shoe inserts, where the pressure face of the shoe includes the smooth surface of the honing shoe inserts. The workpiece, the shoe, or both, are moved so that the abrasive face of the tape is brought in contact with the surface of the workpiece. The workpiece is then rotated with respect to the shoe to abrade the workpiece surface. The abrasive tape may be, for example, a coated abrasive, a lapping abrasive, or a nonwoven abrasive. Examples of camshaft and crankshaft microfinishing are described in U.S. Pat. No. 4,682,444 (Judge et al.) and U.S. Pat. No. 4,993,191 (Judge et al.).
After a certain amount of use, the portion of the abrasive sheet or tape contacting the workpiece will begin to degrade or wear out, which can cause irregular finishing of the workpiece. To continue abrading workpieces, it is therefore common to advance the abrasive tape periodically to provide a new abrasive surface to the workpiece. Advancing the abrasive tape in this manner is referred to as “indexing” the abrasive tape. To allow for ease in indexing the abrasive, the abrasive tape or sheet typically is not permanently fixed or adhered to the pressure face.
Although the abrasive tape is typically releasable from the pressure face to allow indexing, it is important to maintain the abrasive tape in position with respect to the pressure face during the abrading process. If the abrasive tape slips, it may not be properly positioned over the pressure face, which may cause the abrasive tape to tear or break. In automated abrading processes, a dislocation of or break in the tape may damage multiple workpieces before the dislocation or break is detected. In addition, if an abrasive tape breaks the manufacturing operation must shut down. Moreover, if the abrasive tape slips such that it becomes significantly displaced with respect to the pressure face, portions of the pressure face may be exposed to the workpiece during abrasion. In this situation, the workpiece may contact the pressure face rather than the abrasive tape during the abrading process, which may cause improper finishing of the workpiece, and may damage both the workpiece and the pressure face.
While there are various ways of reducing slippage of abrasive tape with respect to the pressure face in finishing operations, additional improvements in the releasable engagement between the abrasive tape and shoe are always desired.